Watch colors disappear and merge right before your eyes
Posted by Dave on May 5, 2010 | 12 Comments
One of the most amazing visual illusions is also one of the simplest. It’s called the Troxler effect for Ignaz Troxler, the scientist who discovered it in 1804. To experience it, just stare at the central dot in this figure for 30 seconds or so, with your head about 12 inches from your computer monitor. After a while, the outer ring will simply fade away. There are no tricks; it even works on the printed page. Give it a shot:
(This may not work on small screens like an iPhone. You can probably still experience it if you zoom in so that you only see a small arc along with the dot). Let’s take a poll to see what portion of our readers experience the illusion:
Although the Troxler effect has been known for more than two centuries, scientists still don’t know exactly how or why the effect occurs. Does the brain simply begin to ignore visual information after a certain period of time? Or does the effect occur before it even reaches the brain? Perhaps our eyes just stop sending information to the brain if what they see doesn’t change.
May will be a month of illusions
Posted by Dave on May 4, 2010 | 9 Comments
For the next month, I’m going to be blogging about illusions and the people who create them. So let’s get started. Take a look at the following short movie, following the on-screen instructions. Just watch it once!
This one is based on an illusion by Stuart Anstis, who in turn based it on a very popular illusion by Peter Thompson. Let’s take a poll to see whether it worked:
Some final thoughts on fitness and nutrition
Posted by Dave on April 30, 2010 | 3 Comments
This month spent on fitness and nutrition blogging has been quite different from the previous two months. While AIDS and global population seem like difficult, nearly intractable problems, personal fitness is something that seems attainable. Even though many people are overweight and out of shape, others have done amazing things.
I have a running partner who regularly participates in ultra-long races. A few weeks ago, he completed a 50 kilometer trail run, and last month, a 50-mile run. On MyFitnessPal, there are women who have lost 50, 80, 100 pounds. So clearly it’s possible for some people to take charge of their own health and fitness.
So how did I do this month? This graph charts my weight over the course of the month:
I ended up losing 6 pounds, even though I was only on a “diet” for one week, when I attempted to follow the DASH guidelines for reduced fat and sodium. That gives me a BMI of 28.1, which is still considered overweight. I’d have to get down to 194.7 pounds to be “normal” weight. Why did I lose weight? It may be that just the act of recording everything I ate made me a little more conscientious. I’d think, “do I really need a snack right now?” and often the answer would be no. The chart below summarizes my nutrition intake for the past month:
Battle of the diets: Mediterranean versus DASH
Posted by Dave on April 28, 2010 | 12 Comments
It seems like every few months we hear about some new diet that is supposed to help us melt away the pounds and add years to our lives. But how different are these diets, really? I’ve already discussed studies suggesting that the DASH diet does indeed appear to decrease risk of heart disease and reduce blood pressure.
So I decided to look into another diet that’s gotten a lot of coverage in the media: the Mediterranean diet. The concept of the Mediterranean diet is that people in nations around the Mediterranean typically share similar diets, and also seem to live longer than people in other places. The traditional diet is high in vegetables, legumes, fruits, nuts, cereals, olive oil, and fish, with a moderate consumption of dairy and alcohol. Red meat and poultry, and foods high in saturated fat, are avoided.
The diet has been widely studied; a typical study was led by Antonia Trichopoulou in 2003. The researchers surveyed 22,043 Greek adults about their eating habits and followed them for almost 4 years. Over that time period, 275 died; what Trichopoulou’s team wanted to know if those who did a better job adhering to a Mediterranean diet were less likely to die. So, as in the DASH study I discussed last week, they created a scoring system. Respondents got a point for how much they ate of each of the items in the list, compared to the average. For example, if you ate more vegetables than average, you got 1 point, but if you ate fewer fruits and nuts than average, you didn’t get a point. Scoring was reversed for meats and poultry, as well as for potatoes and eggs.
A week on a low-sodium, low-fat diet
Posted by Dave on April 27, 2010 | 7 Comments
A couple weeks ago I had a bit of a scare regarding my blood pressure. A drug-store machine had measured it at 144 over 93, which put me squarely in the range considered “high blood pressure.”
But a subsequent visit to the doctor allayed my fears. The doctor’s reading was just 122 over 68, which he said was “very good.” But I decided that in this month of writing about fitness, it would still be interesting to try a diet designed to lower blood pressure. It’s called DASH, and focuses primarily on reducing sodium and saturated fat consumption. It’s been shown to significantly reduce blood pressure in clinical tests. Women who follow a diet similar to DASH have reduced chances of dying from stroke or heart disease over the long term.
The initial DASH guidelines call for consuming no more than 2300 milligrams of sodium (about one teaspoon of salt) per day. Saturated fat should be 13 grams or less. I had been consuming about 3500 mg sodium and 45 g saturated fat. I decided that 2500 mg sodium and 22 g saturated fat would be my goals for the week — a 29 percent reduction in sodium and over a 50 percent reduction in saturated fat.
In the end, I averaged 2,367 mg sodium and 20 g saturated fat per day, so I succeeded. But it was a bit more difficult than I expected. My usual lunch and snack alone had 21 g of saturated fat an nearly 1,000 mg sodium. Chocolate—even tiny portions—rich in saturated fat, had to be cut. Cheese had to be used sparingly or not at all. I resolved not to use special low-fat or low-sodium products that I didn’t already use.
If I were to attempt the full-scale DASH, I’d need to cut sodium almost in half, and reduce saturated fat to 16 g (if you consume less sodium, you get a little more saturated fat). I think it would be difficult to do that without using special foods. These graphs show how my diet changed on DASH:
A day at McDonald’s vs. a day on DASH
Posted by Dave on April 23, 2010 | 3 Comments
This week I’ve been trying to eat according to the DASH guidelines for lowering blood pressure. It actually hasn’t been too difficult — partly because I’m not following their strictest guidelines, which call for just 1300 milligrams of sodium and 16 grams of saturated fat a day. I’ve been shooting for 2300 milligrams of sodium and 22 grams of saturated fat.
In 2003 I tried a somewhat different “diet,” which in some ways was more difficult to follow, even though it only lasted one day. My son Jim (then age 11) and I ate every meal at McDonalds for an entire day (yes, this was before Super Size Me). We recorded the experience on the web, and the site is still live — click here to see it.
I thought it would be interesting to compare my day at McDonalds to a typical day on DASH. This table compares my intake on March 1, 2003 and April 19, 2010, my first official day of DASH:
Helping kids eat better by changing school lunches (Part 2)
Posted by Dave on April 22, 2010 | 5 Comments
Yesterday I discussed two studies on school lunches in California — one showing that students bring lunches from home tended to eat healthier foods, and one showing that kids will keep buying food at school even when the only option is healthy foods.
But both of these studies had flaws. The first study was conducted before California revised its school lunch policies to healthier options. It didn’t account for the possibility that parents who want their kids to eat healthier might have noticed that food options at school were bad and made their kids bring lunch from home. The second study didn’t look at what kids actually ate.
A 2008 study by Karen Weber Cullen, Kathy Watson, and Issa Zakeri addressed all of these issues. The researchers took a look at three middle schools in Texas both before and after the state’s school lunch program was improved. In the fall of 2004, Texas restricted the portions of high-fat and high-sugar snacks and sweetened drinks. They also allowed no foods with more than 28 grams of fat per serving, with the highest-fat foods served no more than twice a week. Serving size of “high-fat vegetables” like french fries was limited and restricted to three servings per week.
In 2001, before the new rules went into effect, experimenters visited schools during lunch and asked randomly-sampled tables of students to record what they had eaten that day. They returned in 2002, when some food restrictions had been put into place, and again in 2005, when the full set of restrictions had been enacted, in addition to removal of all sugary drinks from the schools and shutting off all vending machines during lunchtime.
Did the students eat healthier? Here are some of the results:
Helping kids eat better by changing school lunches (Part 1)
Posted by Dave on April 21, 2010 | 8 Comments
Last year a study was released suggesting that kids who bought lunch at school tended to eat less healthy foods than kids who brought their own lunch from home. Since the National School Lunch Program in the US is supposed to encourage children to eat better, this was quite a blow. If kids don’t eat better when buying school lunches, than what’s the point of government subsidizing lunches in the first place? Is the government just bankrolling an obesity epidemic?
The study, by Theresa Hastert and Susan Babey, compiled the results of of phone surveys of 2,774 adolescents in California schools in 2005. The students were asked how often they had brought lunch to school each week, and how many servings of various foods they’d had the previous day (categories included fruits, vegetables, fried potatoes, soda, and sugary foods). Here are some of the results:
Kids who brought their own lunches ate significantly less of the bad stuff and significantly more fruits and vegetables, which makes school lunches look pretty bad. But there are a few problems with the study. As far as I can tell, the researchers didn’t control for socio-economic status. They didn’t ask whether the students were buying school lunches off campus, at fast-food restaurants. And perhaps most importantly, as the authors acknowledge, the study was conducted the year before the state of California adjusted its school lunch problem to remove some of the least-healthy options.
What happens when schools make some attempts to direct children to healthier foods?
False alarm on high blood pressure? I’m doing the DASH anyways
Posted by Dave on April 20, 2010 | 2 Comments
Last week I posted that I probably have high blood pressure: With a drug store reading of 144 over 93, and a couple earlier measurements that were almost as high, it seemed inevitable that a doctor’s visit would confirm that I do have high blood pressure.
Yesterday was the big day, and instead of confirming my assessment, my doctor said that I actually have “very good” blood pressure of 122 over 68. It’s not bad, but technically a systolic blood pressure of over 120 counts as “prehypertension,” so arguably I’m not out of the woods yet.
The doctor also gave me some advice I’d heard before: For the best results I should buy my own blood pressure gauge and test my pressure at varying times of the day over an extended period of time. So I’ve ordered one and I’ll give it a shot when it arrives.
Despite this diagnosis, I’m still going to give a version of the DASH diet a try—I’d like to see what it entails. Over the first two weeks of the month, I averaged about 3,500 mg of sodium and 42 g of saturated fat per day. That’s about three times what’s recommended on the DASH diet.
This week I’m going to try to reduce that to about 2500 mg of sodium and 22 g of saturated fat — still more than the full DASH guidelines allow. Yesterday, I just about managed it, eating about 1800 mg of sodium and 18 g of saturated fat. I’ve cut out my daily snack of chocolate-covered raisins and replaced it with yogurt and fruit. At lunch, I’m forgoing cheesy microwave enchiladas and instead having a light taco salad with no tortilla chips and very little cheese. Yesterday’s dinner was pretty standard but tonight we’re having hot dogs, and I’m going to have to skip the cheese and mayo and just use ketchup, mustard, and pickles as toppings. There’ll be no butter on my mixed-veggie side dish either.
Quick links: Real-world exercise and nutrition
Posted by Dave on April 19, 2010 | Comments Off
I just have time for a couple quick links today.
First, an article in the NY Times about whether exercise can actually help you lose weight. Short answer: Probably not, but it may help you keep the pounds off. Click here to read the whole thing.
Second, I’ve done a podcast about my post last week on whether diet can be used to control blood pressure over the long term. Every week Razib Khan, Kevin Zelnio and I discuss an article we’ve covered on one of our blogs, and this week it was my turn. Click here to listen to the podcast online. Or if you’d like to subscribe to the podcast, click on this link or just visit iTunes and search for “ResearchBlogCast.”
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The Daily Monthly is Dave Munger's multi-layered exploration of ideas and issues affecting all of us today.
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